textproduct: Quad Cities

KEY MESSAGES

- Training storms tonight into early Friday morning with flash flooding more in the spotlight, with an isolated severe threat of primarily localized winds. Uncertainty on the zone of heaviest rain location.

- Active weather pattern continues into the weekend, with greatest storm coverage at night into the morning. Due to successive rainfall events, additional totals of 2 to 4 inches by Saturday morning are favored with localized higher values likely (70%), continuing the flash flood threat.

SHORT TERM /THROUGH SATURDAY/

Issued at 310 PM CDT Thu Aug 13 2026

In the wake of the earlier MCS, we remain in a somewhat "worked over" environment. The 850 mb temperature and moisture gradients remain draped west to east generally near the I-80 to U.S. Highway 30 corridors. As gradual but persistent warm air advection (WAA) continues along that and taps into 500-1000 J/kg of MUCAPE, festering scattered showers and storms (~30% coverage) should continue in or near that zone through the rest of the daytime hours. Severe potential is limited through that time with very marginal mid-level lapse rates.

For this evening through early Saturday morning, this is when the convective coverage should be higher, expected to peak late evening and overnight. This will be driven by that continued warm air advection and moisture transport in the low-level jet layer, impressively high moisture (PWATs around or slightly over two inches), as well as a couple low amplitude short wave impulses. These attributes favor a west-to-east training setup but with uncertainty on the latitude, as well as how early it ramps up, with a wide breadth in CAM solutions from mid-evening through very late tonight. But with the environment, one to three inches are highly likely in that zone that is to be a couple counties wide from north-to-south, supported by HREF and REFS probability matched mean QPF solutions (account for uncertainty in CAM exact locations). Basically 20-40% of CAMs show some narrow swaths of three plus inch amounts in the zone from near Highway 30 to just south of I-80. These amounts, and especially rates with this high PWAT environment, may be enough on wet ground to result in flash flooding, hence the watch. It was expanded to include the Iowa U.S. Highway 20 corridor due to the north being within the envelope of uncertainty.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 310 PM CDT Thu Aug 13 2026

Friday Evening onward...Convective coverage should be diurnally waning into the midday. Boundary placement should make for high temperature variance from north to south. Timing the next ridge-riding short wave will be likely late day into the evening. The convective mode and coverage for Friday night is highly uncertain, with some CAM signal of a forward-propagating MCS, which would bring at least a scattered damaging wind threat. Regardless of mode, heavy rain to a water sensitive CWA resulted in us extending the Flood Watch.

Saturday through Wednesday...Latest ensemble and upper jet trends suggest the upper ridge and heat dome to get pressed eastward temporarily maintaining the ring of fire for the weekend with the local area precariously near the periphery through at least Sunday. Storm chances will continue as well with high dew point air, but then some signs early next week of upper ridge retrogrades, allowing for more of a northwest flow push down the upper Mississippi River Valley. A resultant drier and cooler Monday would be much welcome by then.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1255 AM CDT Fri Aug 14 2026

Rounds of sctrd showers/thunderstorms will plague the area into Friday morning, but are occurring in linear bands with coverage and many of the TAF sites might not be affected til later Friday morning. Best chance will be BRL overnight into Fri AM with sctrd storms pushing that way for temporary bouts of MVFR to IFR conditions. Ongoing general easterly sfc winds of 7-12 KTs north of a boundary to the south should help prevent dense fog this Friday morning, but there will be areas of lighter fog. Friday morning expect sctrd storms to continue especially with the new activity taking off acrs southwest IA into NE. Then maybe a midday to mid afternoon lull before expect sctrd convection to increases again into Friday evening. But MVFR clouds will look to hang on for much of the afternoon and into the evening. The active pattern and it's impacts to aviation unfortunately look to continue.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Flood Watch through Saturday morning for IAZ040>042-051>054- 063>068-076>078-087>089-098-099. IL...Flood Watch through Saturday morning for ILZ007-009-015>018- 024>026-034-035. MO...Flood Watch through Saturday morning for MOZ009-010.